An optical sensor for the selective detection of substances and for detecting changes in the refractive index in measurement substances is known from International Patent Application WO 86/07,149. Very high measuring sensitivities can be attained with such an arrangement.
German Patent 3,723,159 discloses a chemical sensor that by means of a selective matrix on a waveguide film induces interactions between the selective matrix and the medium containing the substance and brings about measurable physical changes.
International Patent Application WO 89/07756 discloses an integrated optical interference method for the selective detection of substances and liquid and gaseous samples that achieves high sensitivity with a single film- or strip-type waveguide.
It is a failing of these various arrangements that the waveguide, at best provided with a grating and a sensor layer, is used only as a single component; in other words, the functional sensor comprises a combination of components of the integrated optics (such as waveguides) and discrete optics (such as lasers, lenses, photodetectors, mechanical parts and measuring means). The attendant disadvantages are that it is difficult to adjust, is insufficiently stable, and is highly susceptible to external parasitic induction. Moreover, for many applications, the sensor arrangements take up too much space. Complete systems constructed in this way are also very expensive.